1. Field of the Invention
The present invention relates to a mowing apparatus which has two cutting wheels each having a plurality of edges at the outer periphery thereof, which are oscillated to each other to mow grass or sprig or the like as scissors. This invention can be embodied in portable type mowers or trimmers, shoulder type mowers or trimmers, or vehicular type mowers or trimmers (including mowers or trimmers mounted on a truck or the like). Further, this invention can also be embodied in vehicle type or push type lawn mowers, hedge trimmers, edgers, or soy or barley reapers. Furthermore, the apparatus of this invention can also be used as an attachment for a construction machine or an industrial machine.
2. Description of the Prior Art
In prior-art mowing machines for mowing grass or weeds, for example as shown in FIG. 1, a single rotary cutting wheel 10 having a number of cutting edges 10a at the outer periphery thereof is rotatably supported by a bearing case 12 (cutter support body) and driven by an engine 13 via a transmission shaft rotatably passed through a hollow pipe 14 connected between the bearing case 12 and the engine 13. A handle 15 including a first grip 16 is fixed at roughly the middle of the hollow pipe 14, and a second grip 17 is directly fitted onto the hollow pipe 14 so that the worker can swing the cutting wheel 10 to and fro by gripping the grips 16 and 17 by both hands.
When the worker grips the two grips 16 and 17 and swings the hollow pipe 14 to and fro, grass can be mowed by the cutting wheel 10 driven by the engine 13 at a relatively high speed.
In this prior-art mowing machine, however, since only the single cutting wheel 10 rotated at a relatively high speed, there exist various problems such that pebblestones may be kicked off and soft grass cannot be well mowed even when the cutting wheel 10 is moved violently to and fro.
In view of the problems in the prior-art mowing machine, the applicant of this application has been proposed an improved mowing apparatus which is shown in EP patent application No. 0,257,566. Specifically, as clearly shown in FIGS. 2, 3 and 4, the proposed mowing apparatus comprises a pair of upper and lower pivotal cutting wheels 20 and 21 which are superposed with each other. These two wheels are adapted to reciprocatively rotate in two mutually opposite directions (clockwise and couterclockwise) through a predetermined angle in order to mow grass between two cutting edges 20a, 21a, formed along each outer periphery of the two cutting wheels 20 and 21. That is to say, in this apparatus, grass can be cut off in a shearing mode as with a pair of scissors.
In this prior-art apparatus, a transmission shaft 18 passing through the hollow pipe 14 and driven by an engine 13 is rotatably supported by a bearing provided on a junction point between the bearing case 12 and the hollow pipe 14. At the lowermost end of the transmission shaft 18, a first bevel gear 19 is fixed. An intermediate shaft 22 is rotatably supported vertically within the bearing case 12 through bearings 22a, 22b. A second bevel gear 23 which is in mesh with the first bevel gear 19 is fixed on the intermediate shaft 22. A small spur gear 24 is formed on the intermediate shaft 22. Additionally, a cam shaft 25 is also rotatably supported within the bearing case 12 through bearing 25a, 25b and a large spur gear 26 is fixed to the cam shaft 25 so as to be in mesh with the small spur gear 24. Further, two circular and eceentric cam plates 27 and 28 are fixed to the cam shaft 25 with keys. Each of two upper and lower annular connecting rods 30 and 31 is fitted to each of the cam plates 27 and 28, respectively via each of two bearings 32 and 33.
A pivotal cutting wheel shaft 35 is also rotatably supported vertically within the bearing case 12. An upper arm 37 is fixed to at one end thereof the uppermost end of the pivotal cutting wheel shaft 35, and the other end of the upper arm 37 is pivotably linked through a pin 38 to a projecting end of the upper annular connecting rod 30. Further, a lower cutter wheel support plate 39 is fixed to the shaft 35.
On the other hand, a cylindrical member 41 formed with a lower arm 43 and an upper cutter wheel support plate 45 is rotatably fitted around the pivotal cutter wheel shaft 35. An end of the lower arm 43 is also pivotably linked through a pin 42 to a projecting end of the lower connecting rod 31. Further, the upper cutting wheel 20 is fixed to an upper cutting wheel support plate 45 as shown in FIGS. 3 and 4.
In this mowing appratus, the cam shaft (25), the upper and lower cam plates (27, 28), the upper and lower annular connecting rods (30, 31), the bearings (32, 33), the upper and lower arms (37, 43), the pivotal cutting wheel shaft (35) and the cylindrical member (41) constitute a rotational motion converting mechanism which converts rotational motion supplied from a motive power source into two oppositely and reciprocatingly rotational motions of two superposed cutting wheels.
In operation, when the engine 13 is driven, rotational motion is transmitted to the cam shaft 25 by way of the transmission shaft 18, the first bevel gear 19, the second bevel gear 23, the small spur gear 24 and the large spur gear 26, so that the cam shaft 25 is rotated. Therefore, the two circular eccentric cam plates 27 and 28 fixed to the cam shaft 25 is also rotated, so that the two connecting rods 30 and 31 are driven reciprocably to and fro in FIG. 3. In this case, since the connecting rods 30 and 31 are located in radially symmetrical positional relationship to each other with respect to the central axis of the cam shaft 25, the two arms 37 and 43 connected to the two connecting rods 30 and 31 respectively are driven in two opposing directions, respectively. As a result, the two upper and lower pivotal cutting wheels 20 and 21 are mutually and reciprocatingly rotated through a small angle toward two different directions, respectively, to shear off grass caught between two cutting edges 20a, 21a of the upper and lower pivotal cutting wheels 20 and 21. Therefore, it is unnecessary for the worker to chop grass by swinging the machine as in the conventional machine, because the machine according to the present invention mows grass in shear mode as scissors.
The proposed mowing apparatus could successfully solve, the problems in the prior-art mowing machine as described above, and further have the additional advantages in its operational ability and cutting efficiency. However, nevertheless the advantages of the proposed mowing apparatus, the inventors of this application further improved the apparatus in order to simplify the structure thereof, to attain cost reduction in manufacturing by reducing the number of assembling parts thereof, and make adjustment of the rotation angle easy.